This invention relates to a flying spot scanning system for communicating video information to a scanned medium, and more particularly to a scanning system which utilizes a multi-faceted rotating polygon for controlling the scanning cycles.
Much attention has been given to various optical approaches in flying spot scanning for the purpose of imparting the information content of a modulated light beam to a scanned medium. Galvanometer arrangements have been used to scan the light across a document for recording its information content thereon. Such arrangements have included planar reflecting mirrors which are driven in an oscillatory fashion. Other approaches have made use of multifaceted mirrors which are driven continuously. Various efforts have been made to define the spot size in order to provide for an optimum utilization of the scanning system.
In copending U.S. patent application Ser. No. 309,861, filed on Nov. 27, 1972, now U.S. Pat. No. 3,867,571 and assigned to the assignee of the present invention, a flying spot scanning system is provided which does not have constraints imposed upon the spot size and other relationships of optical elements within the system which are not always desirable. As taught therein, a finite conjugate imaging system may be in convolution with the light beam and the rotating polygon. A lens, in series with a convex imaging lens between the light source and the polygon provides this arrangement. The rotation of the polygon is synchronized in a predetermined relation to the scan rate used to obtain the video signal.
In order to determine the scan rate with a correctness and accuracy to insure this predetermined relationship, a suitable start/stop of scan detection scheme must be employed. It is thus an object of the present invention to provide a flying spot scanning system of this type with a start/stop of scan detection arrangement appropriate to achieve the necessary synchronization of elements within the system.
It is a further object of the present invention to provide a spot scanning system which utilizes a multifaceted rotating polygon for controlling scanning cycles.
It is yet another object of the present invention to provide a spot scanning system which provides an effective uniform spot size at the contact loci of the spot with the scanned medium.
It is still another object of the present invention to provide a spot scanning system which assures a minimization of optical distortion through a predetermined synchronization of system elements.
It is another object of the present invention to provide a spot scanning system which utilizes a start/stop of scan detection arrangement which substantially matches the convolution of imaging elements which focus the flying spot at the surface of the scanned medium.
Other objects of the invention will be evident from the description hereinafter presented.